1. Field
The embodiments discussed herein are related to a technique for controlling allocation of data that is allocated to a plurality of disk nodes in a distributed manner.
2. Background
Recently, computers have realized higher speeds and more advanced functions. Also, the scale of an entire computer system has increased with an increase in the variety of businesses using the computer systems. In a large-scaled computer system, data is allocated to a plurality of storage devices in a distributed manner. In such a distributed storage system, the storage device is managed in a corresponding relation to a logical volume. When accessing data in the storage device, a node performing the access designates the position of the data in a logical volume. Then, the node managing the storage device determines the data in the storage device, which corresponds to the designated data position in the logical volume, and makes access to the relevant data.
In the above-described distributed storage system, various performances of the entire computer system are affected by how data is allocated to the storage devices. For example, if accesses are concentrated on a particular storage device, this may cause, for example, a delay in the data access. To realize efficient data access, there is known a technique of moving a logical volume based on a resource amount and a load of each node so that appropriate data allocation is obtained. See Japanese Laid-open Patent Publication No. 2003-296039, for example. By using such a technique, data can be allocated to a plurality of storage devices with higher processing efficiency in the large-scaled distributed storage system.
A larger scale of the distributed storage system improves a processing capability of the system on the one side, but increases a consumption of power on the other side. A function of saving power in a computer can be realized by a technique of shifting an operation to a power saving mode when there is no access to any storage for a certain time. See Japanese Unexamined Patent Application Publication No. 2000-293314, for example. The power consumption can be reduced by turning off power supplied to a magnetic disk by utilizing the power saving mode.
However, the data reallocation techniques hitherto proposed for an improvement of performance are intended to improve the data processing performance without taking into consideration an improvement of environmental performance, such as a reduction of the power consumption. For that reason, the power consumption in the entire system cannot be reduced.
The technique disclosed in Japanese Laid-open Patent Publication No. 2000-293314 can reduce the power consumption in a single storage. In the distributed storage system, however, a series of data is distributively allocated in many cases for the purpose of increasing speed and reliability of data access. In that case, the data access is substantially evenly performed among a plurality of storage devices. Even when the technique disclosed in Japanese Laid-open Patent Publication No. 2000-293314 is directly applied to each of the storage devices in such a computer system, a time slot in which the supply of power can be turned off rarely occurs and an effective reduction of the power consumption cannot be expected.
A technique disclosed herein addresses the problems described above, and intends to realize data allocation suitable for reducing the power consumption.